The electronics community generally, and the telecommunications industry particularly, are constantly striving for higher frequencies of operation. In order to meet the expected demand for broadband communications such as in-home, high density video and interactive computer services, it is necessary to develop reliable methods of modulating signals in the 10 Gb/s range. One device which is capable of this is a Mach-Zehnder phase modulator, based on an interferometric configuration, which converts phase modulation into intensity modulation. The phase of the optical beam travelling through a first arm of the interferometer is altered relative to the phase in the second arm by applying an appropriate modulating voltage to an electrode associated with the first arm. In one such configuration the modulating voltage is applied to each arm in an equal, push-pull relationship for optimum power utilization. A III-V Mach-Zehnder modulator requires up to three volts peak-to-peak per arm at the modulating frequency for equal push-pull operation. Silicon, the traditional material for integrated circuits, is unable to satisfactorily meet these high speed requirements and, as a result, III-V alloy devices such as GaAs MESFETs have been utilized.